Cynomolgus macaques (Macaca fascicularis) will be maintained on a semipurified diet (SPD) containing 1.2 mg of cholesterol/Kcal and 43% of the calories as fat (mainly butter). After 6 months, the monkeys will be randomly assigned to three groups: (a) initial controls, (b) SPD with cholesterol content reduced to 0.34 mg/Kcal for the succeeding 18 months (positive controls), and (c) same regimen as for group b but with the addition of alfalfa saponins. Plasma lipid levels as well as the extent of aortic and coronary atherosclerosis will be determined.